How does expect in chai work with a text string?

Question

I am trying to understand expect behaviour in chai.js. I have the code to check if the login fails with invalid credentials. This is my code:

describe('Login', function() {
  before(function(done) {
    driver.get('https://pluma-dev.herokuapp.com/client-sign-in').then(done);
  });
  it('Login with Incorrect credentials', function( done ) {
driver.findElement(webdriver.By.name("username")).sendKeys("[email protected]");
      driver.findElement(webdriver.By.name("password")).sendKeys("123"); 
      driver.findElement(webdriver.By.className("client-onboarding-signin-btn")).click().then(function(){
      driver.findElement(By.css(".has-error")).getText().then(function (text) {
        console.log(text);
        try{
                expect(text).to.be.a("Invalid email or password");
                done();
        } catch (e) {
                done(e);
        }

      });

});

    });

});

according to my understanding this test case should pass because i am expecting invalid username and password and got the same. However, it throws an Assertion error. That is, 1) Login Login with Incorrect credentials: AssertionError: expected 'Invalid email or password' to be an invalid email or password

Answer 1

You are using the wrong assertion. You want to use:

expect(text).to.equal("Invalid email or password");

.to.be.a (which really is just a call to the assertion named a) asserts that the value has a certain type. Here is some code illustrating the difference:

const expect = require("chai").expect;

it("a", () => expect("foo").to.be.a("foo"));
it("equal", () => expect("foo").to.equal("foo"));
it("correct use of a", () => expect("foo").to.be.a("string"));

The first test will fail. The 2nd and 3rd are correct usages, so they pass.

You can find the documentation for a here.